Many electronic apparatus typically include coil components. Especially for mobile devices, coil components may have a chip form and may be surface-mounted on a circuit substrate included in the mobile devices. As an example of the prior art, Japanese Patent Application Publication No. 2006-324489 disclosed a chip coil including a helical conductor that is embedded in a hardened insulating resin and at least whose one end is coupled to an external electrode. The helical direction of the conductor is arranged in parallel with the surface of a substrate on which the coil is mounted.
As another example, Japanese Patent Application Publication No. 2014-232815 disclosed a coil component including a resin insulator, a coil-shaped internal conductor provided inside the insulator, and an external electrode electrically coupled to the internal conductor. The insulator is made in a cuboid shape with the length L, the width W, and the height H, where L>W≥H. The external electrode includes an conductor provided at each end of a plane perpendicular to the height H direction of the insulator as viewed in the length L direction. The internal conductor has a coil axis that is parallel with the width W direction of the insulator.
In the above-mentioned prior arts, insulators and conductors are alternately layered in the height direction using a photolithography and/or plating technique in order to obtain the coil component.
In recent years, miniaturization of components advances and so too with conductors and their sectional areas included in the components. Consequently it is very important to prevent deterioration of electric characteristics of the conductors while ensuring insulation between the conductors. Compared to electric components in which insulators are made of ceramics or the like, electric components in which insulators are made of resin are more likely to be affected by environments and especially oxidation of conductors included therein cannot be ignored as the miniaturization of the conductors advances.